Controlling access point transmit power based on access terminal ranking / Qualcomm Incorporated

Title: Controlling access point transmit power based on access terminal ranking.Abstract: Transmit power for an access point is controlled based on measurement reports received by the access point from one or more access terminals that are not currently being served by the access point. In some aspects, transmit power is controlled based on the number of received messages that correspond to a particular event. In some aspects, transmit power is controlled based on the contents of the received messages. For example, the access point may use signal strength information included in the messages to determine a level of transmit power that mitigates interference at a defined subset of reporting access terminals. ...

The Patent Description & Claims data below is from USPTO Patent Application 20120046063, Controlling access point transmit power based on access terminal ranking.

CLAIM OF PRIORITY

This application claims the benefit of and priority to commonly owned U.S. Provisional Patent Application No. 61/306,885, filed Feb. 22, 2010, and assigned Attorney Docket No. 101067P1, the disclosure of which is hereby incorporated by reference herein.

CROSS-REFERENCE TO RELATED APPLICATION

This application is related to concurrently filed and commonly owned U.S. patent application Ser. No. 13/030,509, entitled “CONTROLLING ACCESS POINT TRANSMIT POWER BASED ON EVENT-TRIGGERED ACCESS TERMINAL MESSAGING,” and assigned Attorney Docket No. 101067U1, the disclosure of which is hereby incorporated by reference herein.

BACKGROUND

This application relates generally to wireless communication and more specifically, but not exclusively, to controlling access point transmit power.

Introduction

A wireless communication network may be deployed over a geographical area to provide various types of services (e.g., voice, data, multimedia services, etc.) to users within that geographical area. In a typical implementation, macro access points (e.g., each of which provides service via one or more cells) are distributed throughout a macro network to provide wireless connectivity for access terminals (e.g., cell phones) that are operating within the geographical area served by the macro network.

As the demand for high-rate and multimedia data services rapidly grows, there lies a challenge to implement efficient and robust communication systems with enhanced performance. To supplement conventional network access points (e.g., to provide extended network coverage), small-coverage access points (e.g., low power access points) may be deployed to provide more robust indoor wireless coverage or other coverage to access terminals inside homes, enterprise locations (e.g., offices), or other locations. Such small-coverage access points may be referred to as, for example, femto cells, femto access points, Home NodeBs, Home eNodeBs, or access point base stations. Typically, such small-coverage access points are connected to the Internet and the mobile operator's network via a DSL router or a cable modem. For convenience, small-coverage access points may be referred to as femto cells or femto access points in the discussion that follows.

In a co-channel or shared carrier deployment of femto cells such as Home Node Bs, there is a need to protect non-Closed Subscriber Group access terminals (also denoted as non-allowed access terminals or macro access terminals) from interference from Home NodeBs by limiting the transmit power of the Home NodeBs for pilot, overhead, data, and other channels. This transmit power control may be referred to as Home NodeB power calibration. One goal of a transmit power calibration algorithm is to strike a balance between Home NodeB coverage provided to served access terminals (e.g., home access terminals) and limiting the interference impact on non-served access terminals (e.g., macro access terminals or other femto access terminals).

Some conventional transmit power calibration schemes are based on measurements made by a downlink receiver (e.g., a Network Listen Module) at the Home NodeB. This calibration is based on the assumption that nearby home access terminals and nearby macro access terminals will see the same or similar RF conditions as the Network Listen Module. This assumption is not fully accurate, however. Consequently, Network Listen Module-based transmit power calibration suffers from two mismatch conditions.

First, there may be an RF mismatch condition. For example, a Home NodeB placed near a window may see significantly higher macro interference than a home access terminal which may be predominantly away from the window. As another example, a Home NodeB placed in a basement may see significantly lower macro interference than a home access terminal which is predominantly in a higher floor.

Second, there may a deployment mismatch condition. For example, the Network Listen Module is unaware of the macro access terminal traffic surrounding the Home NodeB deployment. A Home NodeB deployed near a busy street corner in a small apartment may affect more macro access terminals than one deployed deep inside a suburban home. This mismatch creates an inaccurate power setting for the Home NodeB in the sense that the power setting may create too much interference for macro users. This interference could lead to excessive inter-frequency handovers or call drops (e.g., when the Home NodeB is placed near a window or near a busy street corner) or could result in inadequate coverage for home access terminals (e.g., when the Home NodeB is placed in a basement or when the Home NodeB is used in a ranch house).

In view of the above, there is a need for effective techniques for protecting macro cell users and other non-allowed users from interference from femto cells while still providing adequate coverage for allowed femto cell users.

SUMMARY

A summary of several sample aspects of the disclosure follows. This summary is provided for the convenience of the reader and does not wholly define the breadth of the disclosure. For convenience, the term some aspects may be used herein to refer to a single aspect or multiple aspects of the disclosure.

The disclosure relates in some aspects to controlling transmit power of an access point. In particular, transmit power for an access point may be controlled based on measurement reports received by the access point from one or more access terminals that are not currently being served by the access point (e.g., access terminals that are in an active call with another access point or that are in idle mode). Such a scheme may be used, for example, to provide transmit power calibration for a femto cell that is operating on a carrier shared with macro access points and/or other femto cells. By effectively learning the boundaries of the femto cell deployment based on received measurement reports, the femto cell may configure its transmit power to limit the number of non-served access terminals (e.g., macro access terminals) affected by interference from the femto cell. Advantageously, such a measurement report-based scheme may mitigate (e.g., eliminate) RF mismatch conditions and/or deployment mismatch conditions that may otherwise exist in a Network Listen Module-based calibration scheme.

The disclosure relates in some aspects to controlling transmit power based on the number of measurement report messages corresponding to a particular event that are received by an access point. In some aspects, an event-based transmit power control scheme may involve: receiving messages at an access point, wherein the messages comprise measurement reports from at least one access terminal that is not currently being served by the access point; identifying a quantity of the messages that indicate the occurrence of a specified type of event; comparing the quantity to a threshold; and controlling transmit power of the access point based on the comparison.

The disclosure relates in some aspects to controlling transmit power based on the contents of received measurement report messages. For example, an access point may use signal strength information included in the messages to rank reporting access terminals and determine a level of transmit power that mitigates interference at a defined subset of the reporting access terminals. In some aspects, a ranking-based transmit power control scheme may involve: receiving messages at an access point, wherein the messages comprise measurement reports from a plurality of access terminals that are not currently being served by the access point; ranking the access terminals based on the received messages, wherein the ranking corresponds to signal conditions at the access terminals that result from transmissions by the access point; designating a subset of the access terminals based on the ranking; and controlling transmit power of the access point to achieve specified signal conditions at the subset of access terminals.

The disclosure relates in some aspects to a network entity that sends measurement reports to an access point that controls transmit power based on received measurement reports. In some aspects, a measurement report handling scheme may involve: receiving measurement reports at a network entity, wherein each of the measurement reports correspond to a specified (i.e., the same) access point; determining that the specified access point controls transmit power based on measurement reports; and sending the measurement reports to the specified access point as a result of the determination.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other sample aspects of the disclosure will be described in the detailed description and the appended claims that follow, and in the accompanying drawings, wherein:

FIG. 1 is a simplified block diagram of several sample aspects of a communication system wherein an access point controls its transmit power based on access terminal measurement reports;

FIG. 2 is a flowchart of several sample aspects of operations that may be performed in conjunction with controlling transmit power of an access point based on access terminal measurement reports;

FIG. 3 is a flowchart of several sample aspects of operations that may be performed in conjunction with controlling transmit power of an access point based on event-triggered measurement reports;

FIG. 4 is a flowchart of several sample aspects of operations that may be performed in conjunction with controlling transmit power of an access point based on a ranking of access terminal measurement reports;

FIG. 5 is a flowchart of several sample aspects of operations that may be performed in conjunction with a handling measurement reports at a network entity;

FIG. 6 is a simplified block diagram of several sample aspects of a communication system wherein an access point uses a multi-stage power control scheme to control transmit power;

FIG. 7 is a flowchart of several sample aspects of operations that may be performed in conjunction with a multi-stage transmit power control scheme;

FIG. 8 is a simplified block diagram of several sample aspects of components that may be employed in communication nodes;

FIG. 9 is a simplified diagram of a wireless communication system;

FIG. 10 is a simplified diagram of a wireless communication system including femto nodes;

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20120223|20120046063|controlling access point transmit power based on access terminal ranking|Transmit power for an access point is controlled based on measurement reports received by the access point from one or more access terminals that are not currently being served by the access point. In some aspects, transmit power is controlled based on the number of received messages that correspond to |Qualcomm-Incorporated